On Thu, 12 Oct 2023 10:10:36 +0530
Ani Sinha <anisi...@redhat.com> wrote:
> > On 11-Oct-2023, at 10:01 PM, Jonathan Cameron <jonathan.came...@huawei.com>
> > wrote:
> >
> > On Wed, 11 Oct 2023 16:23:35 +0530
> > Ani Sinha <anisi...@redhat.com> wrote:
> >
> >> pc_get_device_memory_range() finds the device memory size by calculating
> >> the
> >> difference between maxram and ram sizes. This calculation makes sense only
> >> when
> >> maxram is greater than the ram size. Make sure we check for that before
> >> calling
> >> pc_get_device_memory_range().
> >>
> >> Signed-off-by: Ani Sinha <anisi...@redhat.com>
> >
> > Whilst this is similar to other cases, I can't remember or quickly work
> > out if the 'else' path here is appropriate. Can we add something to the
> > patch description to talk about that?
> >
> > For reference it's:
> >
> > cxl_base = pc_above_4g_end(pcms);
>
> Leaving the alignment adjustments aside, the hotplugged memory devices are
> mapped starting from where the “above_4g” memory ends.
> The cxl memory starts after the region reserved for hot plugged memory
> devices. If there is no hot plugged memory device region (maxmem == mem), the
> cxl memory can start right after where “above_4g” memory ends.
> See also pc_pci_hole64_start() and pc_max_used_gpa().
> I did not want to add any alignment adjustments because I was not sure if it
> would add regression and incompatibility with older machine types.
>
Thanks for explanation.
Acked-by: Jonathan Cameron <jonathan.came...@huawei.com>
>
> >
> >> ---
> >> hw/i386/pc.c | 4 +++-
> >> 1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> >> index f72e2c3b35..948c58171c 100644
> >> --- a/hw/i386/pc.c
> >> +++ b/hw/i386/pc.c
> >> @@ -820,10 +820,12 @@ static void
> >> pc_get_device_memory_range(PCMachineState *pcms,
> >> static uint64_t pc_get_cxl_range_start(PCMachineState *pcms)
> >> {
> >> PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
> >> + MachineState *ms = MACHINE(pcms);
> >> hwaddr cxl_base;
> >> ram_addr_t size;
> >>
> >> - if (pcmc->has_reserved_memory) {
> >> + if (pcmc->has_reserved_memory &&
> >> + (ms->ram_size < ms->maxram_size)) {
> >> pc_get_device_memory_range(pcms, &cxl_base, &size);
> >> cxl_base += size;
> >> } else {
> >
>
